The finding of manganese oxides in Martian rocks power tell us that the Red Planet was once extra Earth-like than before believed. A new paper in Geophysical Research Letters reveals that NASA's Curiosity rover experiential high levels of manganese oxides in Martian rocks, which could indicate that higher levels of atmospheric oxygen once existed on our adjacent planet. This hint of more oxygen in Mars' early on atmosphere adds to other Curiosity findings—such as proof of ancient lakes—revealing how Earth-like our adjacent planet once was.
"The only ways on Earth that we know how to create these manganese materials involve atmospheric oxygen or microbes," said Nina Lanza, a planetary scientist at Los Alamos National Laboratory and guide author on the learn published in the American Geophysical Union's journal. "Now we're considering manganese-oxides on Mars and wonder how the heck these could have shaped."
Lanza uses the Los Alamos-developed ChemCam tool that sits atop Curiosity to "zap" rocks on Mars and study their chemical make-up. This work stems from Los Alamos National Laboratory's knowledge building and operating more than 500 spacecraft instrument for national defense, giving the Laboratory the expertise required to develop discovery-driven instruments like ChemCam. In less than 4 years since landing on Mars, ChemCam has analyzed roughly 1,500 rock and soil sample.
Microbes appear a far-fetched explanation for the manganese oxides at this point, said Lanza, but the thought that the Martian atmosphere restricted more oxygen in the past than it does now seems possible. "These high-manganese resources can't form without lots of liquid water and powerfully oxidizing conditions," said Lanza "Here on Earth, we had plenty of water but no widespread deposit of manganese oxides awaiting after the oxygen levels in our atmosphere rose due to photosynthesizing microbes."
In the Earth's geological evidence, the appearance of high concentration of manganese is an important marker of a main shift in our atmosphere's composition, from comparatively low oxygen abundances to the oxygen-rich ambiance we see today. The presence of the same types of materials on Mars suggests that something similar happen there. If that's the case, how was that oxygen-rich surroundings formed?
"One possible way that oxygen could have gotten into the Martian atmosphere is from the stop working of water when Mars was behind its magnetic field," said Lanza. "It's thought that at this time in Mars' history, water was much additional abundant." Yet without a defensive magnetic field to shield the surface from ionizing radiation, that radiation in progress splitting water molecules into hydrogen and oxygen. Because of Mars' comparatively low gravity, it wasn't able to hold onto the extremely light hydrogen atoms, but the heavier oxygen atoms remained at the back. Much of this oxygen go into the rocks, leading to the rusty red powder that covers the outside today. While Mars' famous red iron oxides require only a mildly oxidizing surroundings to form, manganese oxides require a powerfully oxidizing environment. These consequences suggest that past conditions were far additional oxidizing (oxygen-rich) than before thought.
"It's hard to corroborate whether this scenario for Martian atmospheric oxygen in fact occurred," Lanza added. "But it's significant to note that this idea represents a exit in our understanding for how planetary atmospheres might turn out to be oxygenated." So far, plentiful atmospheric oxygen has been treat as a so-called biosignature, or a sign of existing life.
The after that step in this work is for scientists to improved understand the signatures of non-biogenic versus biogenic manganese, which is straight produced by microbes. If it's likely to distinguish between manganese oxides shaped by life and those shaped in a non-biological setting, that knowledge can be directly applied to Martian manganese observations to improved understand their origin.
The high-manganese materials were establish in mineral-filled cracks in sandstones in the Kimberley region of Gale hollow, which the Curiosity rover has been explore for the previous four years. But that's not the only place on Mars that abundant manganese has been found. The chance rover, which has been exploring Mars since 2004, also lately discovered high-manganese deposit in its landing site thousands of miles from Curiosity, which supports the plan that the conditions required to form these materials were near well beyond-Gale crater.
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